Fuel supply system for internal-combustion engines



April 27, 1948 G. J. ARMSTRONG n AL 2,440,567

FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed Feb. 27,11945 2 Sheets-Sheet 1.

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' mmne G. J. ARMSTRONG El' AL FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed Feb. 27, 1945 2 Sheets-Sheet 2 P/JPLICEMENT NrKE PRESSURE g/ sil;

////I 64 Orman/vtm Passt/az IN T4 AE Pennac Apazv, 194s n UNITED fsTATEs PATENT ottici?. n 2,440,561

FUEL sUrrL srs'rEM ron INTERNAL- coMUsTloN ENGmEs Y George Jeirey Armstrong, Beatrice Naylor, and

l John ,Ernest England l Patrick Dunning, Farnborough,

6 Claims.

The invention relates to a fuel supply system for a reciprocating internal combustion engine in which fuel after passage through an adjustable metering valve or valves is injected into an intake along which air passes to the engine.

It is known that the mass air consumption of the engine, i. e. the air consumption measured in units of mass per unit time, and hence the fuel requirements are dependent on the absolute pressure in the intake manifold, the absolute exhaust back pressure, the temperature in the intake manifold, and the rotational speed of the engine crankshaft. In most engines the exhaust back pressure is nearly the same as and varies with atmospheric pressure, and in controlling the fuel supply the value of theatmospheric pressure may be measured instead of measuring exhaust back pressure directly.

The invention is more particularly concerned with lthe regulation of the pressure` diierence across the metering valve or valves so as to provide for a given adjustment of the valve or valves v the desired relationship (usually approximately` linear) between engine speed and fuel flow, and is a further development of the invention of U. S. application Serial No. 522,352. v

In accordance with the invention a fuel supply system as hereinbefore specified comprises an adjustable pressure regulating valve for regulating the pressure difference across an adjustable metering valve, an element for adjusting the pressure regulating valve in response to changes in the pressure difference generated by an engine driven centrifugal pump through, which fuel is passed from an inlet at or-near the periphery to an outlet at or near the eye and thence direct to the intake manifold.

The forward flow from the outlet oi' the centrifugal pump to the intake manifold gives certain advantages in the present system as compared with any system specifically described in the specification of the aforesaid copending U. S.

(Cl. 12S-119) sure regulating valve l5, chamber I6, passage i1, chamber I8, metering valve I9, passage and discharge nozzle 2|. The discharge nozzle 2| is adjustable by means of a tapered needle 22 in the 'manner described in copending British application No. 9250/43 (U. S. Serial No. 580,028), the needle 22 being for this purpose securedto a diaphragm |20 which is backed by a spring |2| ina 4chamber having a port |22 open to the atmosphere. 'I'he right hand sideof the diaphragm |20 is therefore acted on bywthe pressure of the fuel in the passage 20 while the left hand side is 4acted on by atmospheric pressure and by the pressure applied vby the springv |2|. 'Ihe needle quantity dependent on the stiffness of the spring application.` Thus for example dissolved air sep-l parent from the detailed description read in con-A junction with the accompanying drawings in which Figs. l and 2 are schematicsectional views of alternative systems embodying' the invention.

|2|. If the design of the `exhaust system or the presence of exhaust-driven accessories, such as an exhaust-driven turbo supercharger, renders it no longer possible to assume that the exhaust back pressure is always approximately equal to latmospheric pressure, it may be necessary to measure the exhaust back pressurev directly in-I stead of indirectly through the atmospheric pressure, infwhich case the port |22 may be connected to the engine exhaust, as indicated by the legend in Fig. 1, so ,that the pressure of the fuel in the passage 20 is maintained at a value exceeding the exhaust-back pressure by an amount determined by the pressure exerted by the spring |2| The output of the positive displacement pump is arranged to exceed the maximum fuel requirements of the engine at any operating' speed and to dispose of the excess output a relief valve 23 is provided. The effective area of the metering valve |9 is adjusted by atapered needle 24 whose position is controlled by an assembly of -flexible bellows 25, 28. The bellows 25 is subjected internally to the pressure in the intake manifold 21 through a pipe 28: the bellows 2B is evacuated and anchored to a .temperature responsivev capsule 29 which is connected by the tube 3|! to a thermometer bulb 3| situated inthe -intake manifold and which consequently responds to changes of temperature in the intake manifold. `'I'he operation of the needle 24 and the control assemblyalso forms part of the specification of co-pending Brltish'applicatlon No.

9250 43 (U. S. Serial No. 580.028),

D ven by the same shaft I2 as the positive displacement pump II is a centrifugal pump 33 in which the pressure at its peripher'y is lthe `same as the pressure in the passage I3, which is regulated to a pre-determined value by the relief valve 23, and which generates a pressure difference such that the pressure at the eye`is alwaysless than the pressure at the periphery and in the passage I3. Because it is so arranged that the pressure drop between the passages I3 and 20 is at all times greater than the pressure difference kdeveloped by the centrifugal pump 33, liquid passes through the centrifugal pump from the periphery towards the eye where an outlet into a chamber 34 is provided, liquid from the chamber 34 passing therefrom to passage 35, valve 3B, passage 31 and through passage 20 and discharge nozzle 2| into the intake manifold. Dividing the chamber 34 from the chamber I4y is a flexible diaphragm 38 to which is attached a second diaphragm 39 by a rod 49 carrying a taperedplug 4I, movement of which adjusts the effective area of they pressure regulating valve i5. The diaphragm 39 is subject on the one side to the pressure in chamber I3 and on the other side .to the pressure in a chamber. 42 connected to pipe 20. Consequently, the effective area of the pressure regulating valve I5 will be adjusted by movement of-I the tapered plug until equilibrium is set up between the pressure differences acting in opposition across the two diaphragms 38, 39 which will be set up when the pressure difference across the metering valve I9 is equal to the pressure difference generated by the centrifugal punp 33. By varying the relative areas of the diaphragms 38. 39, the proportionality between these pressure differences may `the engine speed, and the ow through the metering valve I9 will therefore, `for a given adjustment of the metering valve, be proportional to the engine speed.

The valve 36 forming the slow running device comprises a tapered plug 43 secured to a flexible diaphragm 44. The right hand sdeof the diaphragm 44 is acted upon by the pressure existing at the eye of the centrifugal pump, while the left hand side is acted upon by the pressure at the periphery of the centrifugal pump. Secured to the left hand side of the diaphragm 44 is a tension spring 45 whose anchorage is adjustable by a knurled nut 46. Consequently the tension spring tends to hold the plug 43 awayifrom its seating, to open the valve 36 while as the engine speed rises the plug 43 is pressed towards its seating. The plug 43 is arranged to allow leakage when pressed on its seating so that a small flow through thevalve 36 takes place under all operating conditions, thus maintaining a slow flow through the l centrifugal pump 33;

the pressure at the output side of the positive displacement pump I'I at a constant value.

The output of the positive displacement pump II is fed through the passage I3 to a chamber 69 which it leaves through metering valves 5I, 52, 53, entering chamber 54 which it leaves through shown but similar to the discharge nozzle 2| shown in Fig. 1. l"Ilhe effective area of the metering valve 6I is controlled by taperedneedls 51 attached to an evacuated resilient bellows B3 enclosed in a casing 39 to which the intake manifold is connected by a pipe SII, and the metering valve 52 is controlled by a .tapered plug 3l which is connected to an evacuated bellows 32 enclosed in a casing 93 which is vented to theatmosphere at 94. The` third metering valve 53 is adjusted by a tapered needle 65 which is attached to a temperature sensitive element 36 to which isconnected a thermometer bulb (not shown) located in the intake manifold.

The centrifugal pump 33 is one of which the effective radius at which the pressure used for fuel metering is picked up may be varied at will as described in co-pending U. S. application Serial No. 522,352,y now Patent No. 2,407,139, the pump having for this purpose an outlet which vis pivoted eccentrically to the pump casing, and which is rotated by a knurled knob 61. The pressure regulating valve' 55 is adjusted by a tapered plug 63 connected to a link 69 to one end of which is atytachedA a diaphragm 10. The right hand side of diaphragm 'I0 is acted upon by the pressure at 'the eye of the centrifugal pump 33.

An equilibrium adjustment of the pressure regulating valve 55 is established when the pressure on the two sides of the diaphragm 'IIJ balance one anotheni. e., when the pressure difference across the metering valves 5I, 52, 53 is equal to the pressure difference generated by the centrifugal pump 33. To offset the inherent out-ofbalance of.' the type of tapering plug 68 shown, l

a spring 'II abuts against a shoulder on the rod 69. A passage 3| feeds forward from the eye of the centrifugal pump'to the passage 59 through an adjustable slow running jet, indicated at 92.

Though for simplicity no supercharger has been shown in the drawings the invention maylbe embodied in a fuel system for a supercharged engine.

We claim: l. A fuel supply system for injecting fuel into an intake of an internal combustion engine, comprlsing a duct entering .the intake, an adjustable metering valve located in said duct, an adjustable pressure regulating valve also located in said duct lfor regulating the pressure difference across said an intake of an internal combustion engine, com- I prising a duct entering the intake, an adjustable metering valve located in said duct, an adjustable pressure regulating valve also located in said duct for regulating the pressure difference across said metering valve, a positive displacement pump for supplying fuel to said duct, a centrifugal pump through which fuel is passed by said positive displacement pump from an inlet remote from the eye thereof to an outlet nearer the eye and thence to said intake, a pressure-responsive member acted upon by the pressure difference across said i centrifugal pump, a second pressure-responsive pressure regulating valve 33 whence it is supplied member acted upon by the pressure difference across said metering valve, and a connection between said pressure-responsive members and said pressure-regulating valve, whereby said regulatt ing valve is adjusted continuously to maintain the pressure difference across said'A metering valve proportional to the pressure difference, across said same pressure, a pressure regulating valve' in the duct down stream of themetering valve and a pressure-,responsive member connected to the` pressure regulating valve to effect adjustment of the same, one side of said pressure-responsive member being acted upon by the pressure existing at the outlet of the centrifugal pump upstream of the metering valve andV thel other side of said pressure-responsive member being acted upon by the pressure existing downstreamof the metering valvewhereby the pressure across said metering valve lis maintained the same as the pressure across the centrifugal pump.l

4. A fuel supply system as claimed in claim 1, in which the metering valve comprises at least one adjustable element actuated by a member responsive to changes in the absolute pressure and temperature inthe intake and in a pressure equivalent to the exhaust back pressure.

5. A fuel supply system as claimed in claim 1.

in which an adjustable slowrunning valveis in- 40 aardse? terposed between the centrifugal pump and the f intake. l

6.` A system for injecting fuel into the intake of an internal combustion engine, comprising a positive displacement pump for supplying fuel to the intake, at least one adjustable metering valve whose total ilow area is adjusted in response to changes in the absolute pressure and temperature inthe intake and a pressure` equivalent to 'the exhaust back pressure, a centrifugal pump located tojbe fed with fuel from said positive displacement pump from an inlet at the high pressure side thereof to an outlet at the low pressure side thereof and thence to the intake, and pressure.-A l5 regulating means for regulating the pressure drop across said metering valve to maintain the same proportional to the pressure `drop across the cen-V trifugal pump. Y

-GEORGE JEFFREY ARMSTRONG. lBEATRICE NAYLOR. JOHN ERNES'IBA'IBICK DUNNING.

unanimous crrrm 25 The following `references are of record in the vfile of this patent: i

UNITED s'ra'rns PATENTS Number Y Name Date 30 2,224,472 Chandler Dec. 10,1940 2,250,932 Kittler July 29, 1941 2,303,998 Holly. Jr. Dec. V1, 1942 2,341,257 Wunsch -Feb. 8, 1944 2,348,008 Hunt May 2, 1944 l 35 2,374,844 Stokes May 1, 1945 i v FOREIGN PATENTS Number Country Date 429,682 Great Britain June 4, 1935 '523,896

Great Britain July ,25, 1940 

